The present invention relates to monitoring the number of doses of aerosol medication dispensed from an aerosol dispensing assembly. In particular, the invention relates to a dose counter device of the type adapted to be used on an aerosol dispensing assembly, as well as to a method of counting doses of aerosol medication dispensed from such an assembly.
Metered medication dose dispensers, known as “inhalers”, are commonly used for the treatment of asthma and other respiratory conditions. Metered dose dispensers typically take the form of an aerosol dispensing assembly having an aerosol container and a housing for receiving that container. The container includes medicament that is formulated with a suitable propellant that is filled into the container to define an aerosol vial. The container is typically equipped with a dispensing means, fitted by means of a ferrule, such as a valve, in particular, a metered dose valve, comprising an elongate outlet member (e.g., a valve stem) movable between closed and discharge positions, and thus defines a medication dispensing canister. The canister is not refillable, and is disposed of once the medication therein has been dispensed. The dispensing canister is typically used in conjunction with an actuator or housing (which may be reusable) that has a patient port (e.g., a mouthpiece or a port adapted for nasal use). The actuator typically comprises a support block that has a socket adapted to receive the outlet member of the valve on the container, and has an orifice in communication with the socket and the patient port. The dispensing canister and the support block are reciprocally movable relative to each other along an axis to allow the outlet member to move to its discharge position during the operation or firing of the device, thereby dispensing a dose of the medicament from the container. The actuator also typically includes an elongate portion extending opposite the support block and providing a chamber to house at least a portion of the container. There are many related design features of the actuator and the dispensing canister that are employed in order to achieve the desired medicament dispensing performance (i.e., the dispensing of one metered amount or dose of sprayed medication of appropriate particle size distribution each time the dispenser is actuated by a user).
To dispense a dose of medication, an inhaler user normally squeezes or pushes down on the inhaler in an axial direction causing a relative movement of the canister into the actuator towards the support block. It is useful for an inhaler user to know how many doses remain in his or her inhaler (i.e., how much medicament by dosage is in the container of the aerosol dispensing assembly). To this end, a reliable dose counter device and methodology is desired, in order to register how many doses have been dispensed from an aerosol dispensing assembly and in order to inform a user how many more doses still remain to be dispensed. Aerosol dispensing assemblies can vary in configuration, and it would be desirable to provide a dose counter device which is generally universally usable with the various aerosol dispensing assemblies available, and in particular with varying aerosol containers of medications that are available.